1. Field of the Invention
The present invention relates to a semiconductor device having ferroelectric capacitors, such as a ferroelectric random access memory (FeRAM) or a micro-electrical mechanical system (MEMS), and a method of manufacturing the semiconductor device
2. Description of the Related Art
In recent years, the integration density of dynamic random access memories (DRAMs) has increased. As the integration density increases, the capacitance of each element is approaching its lower limit (i.e., the smallest capacitance below which the element can no longer operate). Hence, nonvolatile semiconductor memories having ferroelectric capacitors, such as FeRAMs, are being developed as devices in which elements can operate even at a smaller capacitance. To manufacture a semiconductor memory of this type, ferroelectric capacitors must be formed at a time by using one mask (lPEP) to raise the integration density.
However, the material used for the electrodes of the ferroelectric capacitor, particularly precious metal (Pt or Ir), is far less volatile than is desired. Consequently, metal residue may lie between the upper and lower electrodes of each capacitor if the capacitors are formed at a time by means of reactive ion etching (RIE). The metal residue will induce capacitor leakage, which increases defective bits or defective chips in numbers. Thus, the metal residue will lower the manufacture yield of the products.
In manufacturing a FeRAM having ferroelectric capacitors, metal residue is formed when ferroelectric capacitors are formed at a time, each comprising a lower electrode, a ferroelectric layer and an upper layer. The metal residue induces capacitor leakage, which increases defective bits or defective chips in numbers. This problem is not limited to nonvolatile semiconductor memories such as FeRAMs. Rather, the problem may arise in various semiconductor devices that comprise ferroelectric capacitors.